1. Field of Invention
This invention relates generally to electronic displays and more particularly to forming filter elements on display substrates.
2. Description of Related Art
Electronic displays are used to produce visual output for a number of electronic devices such as television and computer monitors, mobile communication devices, and electronic book devices (e-Readers), for example. Various types of electronic displays are commonly used, including liquid crystal displays (LCD), Organic Light Emitting Diode displays, Electro-wetting displays, and Electrophoretic displays, for example.
LCD displays are an example of a transmissive display that utilizes a color filter to turn what is effectively a monochromatic display into a color display. A thin film transistor (TFT) layer and a color filter layer are generally separately manufactured on glass substrates, which are subsequently aligned and assembled into a display unit. The TFT layer includes a plurality of drivers, each driver being operable to control a small area of the display or picture element (pixel). The color filter layer generally includes red, green, and blue color filter elements that overlay the display pixels and filter the white light to display a color image.
Color filters for LCD displays have been predominantly produced using photolithographic techniques, but thermal laser transfer of colorants or inkjet transfer of colorants onto a color filter glass substrate or even directly onto the TFT layer have also been attempted. By transferring colorants directly onto the TFT layer, the need for subsequent precision alignment of the color filter to the TFT layer is avoided.
Electrophoretic displays are an example of a reflective displays, in which ambient light provides illumination and display pixels are electronically controlled by an underlying TFT to selectively reflect the ambient light to form a display image. Like LCD displays, electrophoretic displays are also essentially monochrome displays. In order to provide a color display, color filter elements may be formed over the reflective display pixels. The color filter elements may cover substantially the entire area of the associated reflective display pixel, or may only cover a portion of the area.
There remains a need for improved methods and apparatus for forming color filters.